1. Field of the Invention
This invention relates to techniques for delivering Web pages from an overloaded or partially functional Web server to a client, and more specifically to a system, method and program for sending to a client a requested document via e-mail or a Push technique after the original session with the client terminates.
2. Description of the Related Art
The Internet, initially referred to as a collection of xe2x80x9cinterconnected networksxe2x80x9d, is a set of computer networks, possibly dissimilar, joined together by means of gateways that handle data transfer and the conversion of messages from the sending network to the protocols used by the receiving network. When capitalized, the term xe2x80x9cInternetxe2x80x9d refers to the collection of networks and gateways that use the TCP/IP suite or protocols.
Currently, the most commonly employed method of transferring data over the Internet is to employ the World Wide Web environment, referred to herein as xe2x80x9cthe Webxe2x80x9d. Other Internet resources exist for transferring information, such as File Transfer Protocol (FTP) and Gopher, but have not achieved the popularity of the Web. In the Web environment, servers and clients effect data transfer using the Hypertext Transfer Protocol (HTTP), a known protocol for handling the transfer of various data files (e.g., text, still graphic images, audio, motion video, etc.).
Overloading is a term that is used when the processing and/or resource capabilities of a system are being used to the point where the system""s efficiency becomes degraded. Programs exist today that can determine whether or not a system is becoming overloaded and to what extent the system resources are being used. For example, Windows 95 operating system has software modules that determine how much of the system resources are being used.
FIG. 1 shows a prior art system for load balancing when a server is overloaded. Server 100 is linked to several servers 101, 102, 103, and a client 110. Since the server 100 is not powerful enough, it splits its work among the other servers 101, 102, 103. A request from a client 110 would be directed by the server 100 to one or more of the other servers 101, 102, 103, depending on which of the servers 101, 102, 103 is less busy. Server 100 tries to balance the work load amongst the other servers. Servers 101, 102, and/or 103 can then communicate directly with the client 110 or respond to the client through the server 100. Essentially, the server splits up its workload amongst the various machines. This is the way that servers presently prevent overloading in server based systems.
Overloaded or partially functional Web servers are a major problem on the Internet. If a client is trying to get Web pages from such a server, the client may either have to wait an unreasonable amount of time to receive the requested pages, or the client may never receive the requested Web pages.
Web servers can get overloaded or become partially functional for many reasons. One cause of overloading results from very high usage of servers at certain times of the day and very little usage at night. It has been observed that Web servers become overloaded during the middle of the day when employees of corporations are taking their lunch breaks and are checking the news from Web servers. Different Web servers get overloaded at different times of the day. For example, a Web server for the Los Angeles Times newspaper may get overloaded from 9:00 a.m. to 5:00 p.m. Pacific Time when people on the west coast are checking the news, but may not be overloaded at other times of the day. Likewise, corporate Web sites may get overloaded during normal working hours, but may be greatly underutilized at nights, during weekends, or during holidays, when most employees are not working.
Overloading is also caused by the sudden very high usage of a reference to a site in a widely read news media (e.g., a reference to a Web site in the Internet edition of the New York Times). This type of overloading happens very often. This happens when a small Web site typically comes into the news because it has made a new product or has made a recent press release. Typically users reach the site by following links from a daily newspaper. For example, a very common occurrence happens when a major newspaper, e.g., the New York Times, publishes an article on a new technology or science or health feature, and the article provides links to other Web pages. Typically, in Web articles, if any other pages are referenced, those pages are provided at the end of the article as links. Internet links are used in Web articles in the same way as Bibliographies are used in printed articles. If a small Web site is cited as a link in an article that has a high volume of readers, the small site which does not have much capacity often gets overloaded.
It is difficult to design a Web site to handle overloading, especially overloading caused by sudden high usage, because it is counterproductive to have a large mainframe machine or a large server handle a relatively small Web site that under normal conditions does not utilize the full processing power of the server machine.
The generation of dynamic Web content, i.e., Web content that is generated by Web servers on the fly upon request (e.g., via CGI scripts, Server side Javascript, or servlets), also consumes a lot of resources and are time intensive and can overload a Web server if multiple clients request dynamic Web content at the same time. These new technologies go beyond just sending static HTML pages.
The HTML specification allows many embedded images in an HTML page. Web servers which have very high number of embedded images have a big overload spike whenever the pages are downloaded with images. This assumes that the images are from the same Web server as the parent HTML file. These sudden increases in the peak load on a Web server are another reason for a Web server to become overloaded or partially functional.
Currently, Web servers have become very complicated, especially e-commerce systems, and they often rely on databases and file servers and other types of servers. A Web server is no longer a single computer. Instead, the Web server is becoming just an interface that has connections to file servers, databases, credit card verification servers, customer database servers, and so forth. Any of these other servers can become incapacitated for various reasons, e.g., the network link is down, a computer is down or overloaded, etc. As a result, the Web server, interacting with a client and these other servers, may be functional, but it may not be totally functional since one or more of the supporting servers are not available for the Web server to perform all of its tasks. As such, the Web server may be temporarily incapacitated or partially functional.
Currently, when a Web server is overloaded or partially functional, the following can occur:
i) The Web client keeps waiting for a requested document to arrive and never gets it. Since the Web server is busy, the Web server can not even send to the Web client an HTTP return code to indicate what went wrong. As such the client waits for the server to return something. Typically, the client has a certain time that it has set up after which if the client has not received a response from a server, it times out. The term xe2x80x9ctime outxe2x80x9d refers to a situation when the Web client has set up a maximum time it is willing to wait for a document to arrive before terminating the request, and that time is reached.
ii) Some servers realize that they have a problem and send an immediate response stating something similar to the following:
xe2x80x9cThis server is experiencing difficulties. Please try again later.xe2x80x9d
iii) The server returns an HTTP error return code.
Any one or more of the above three events causes problems for a client because the user of the client has to remember to go back to the server at a later time to make the request. This is burdensome for the user.
The system, method and program of the invention enables an overloaded or partially functional Web server to keep track of the clients that send requests, and to send the data at a later time in a different session of the network communication. More specifically, the overloaded, or partially functional, Web server carries out any one or more of the following. The Web server sends the requested resource (typically an HTML page) by e-mail or push techniques at a time when it is not overloaded. Alternatively, the Web server sends the basic abbreviated data to the client, such as the text only data; and then sends the full data (the data that includes the inline images or other dynamically generated data) later on via e-mail or push techniques.
The advantages of the invention include, but are not limited to, the following:
i) On the client side, although the client request is not immediately satisfied, the client still gets the resource without the client having to ask for it again.
ii) On the server side, the server""s advantage is that the server can perform load balancing deliberately under its own control. The server can carry out this load balancing using various mechanisms. For instance, the server can regard some users as being more important than others and thus desire to satisfy their requests first. For example, a paying subscriber, such as a client who visits a Web site quite often, may get preferential treatment when the Web server is busy such that the paying subscriber may get immediate results from a request while other clients get the request satisfied at a later time through e-mail.
iii) The possibilities of xe2x80x9cDenial of Servicexe2x80x9d responses is reduced, although they can still occur in extreme circumstances.